Add GitHub Actions workflow (#499)

Author: abetomo

.github/workflows/workflow.yml

@@ -0,0 +1,21 @@
+name: Node CI
+
+on: [push]
+
+jobs:
+  test:
+    name: Test on node ${{ matrix.node-version }} and ${{ matrix.os }}
+    runs-on: ${{ matrix.os }}
+    strategy:
+      matrix:
+        node-version: [8.x, 10.x, 12.x]
+        os: [ubuntu-latest, windows-latest, macos-latest]
+    steps:
+    - uses: actions/checkout@master
+      uses: actions/setup-node@v1
+      with:
+        node-version: ${{ matrix.node-version }}
+    - name: npm install, and test
+      run: |
+        npm install
+        npm test